January 19, 2016 -- On January 15, 2016, the United
States Department of Agriculture’s (USDA) Animal and Plant Health
Inspection Service (APHIS) reported
detection of highly pathogenic avian influenza (HPAI) H7N8 virus in a
commercial turkey flock in Dubois County, Indiana. Subsequently, APHIS
reported detection of low pathogenic avian influenza (LPAI) H7N8 among 8
nearby turkey flocks*. There are nine known subtypes of avian influenza H7 viruses (H7N1, H7N2, H7N3, H7N4, H7N5, H7N6,
H7N7, H7N8, and H7N9); most of these have been LPAI viruses. LPAI H7N8
virus has been detected previously in wild bird surveillance in the
United States, but this is the first instance of HPAI H7N8 virus
detection in poultry.

Avian influenza viruses are classified
as either low pathogenic or highly pathogenic depending upon molecular
characteristics of the virus and the virus’ ability to cause disease and
mortality in chickens in a laboratory setting. Infection of poultry
with LPAI viruses may cause no disease or mild illness (such as ruffled
feathers and a drop in egg production) and may not be detected.
Infection of poultry with HPAI viruses can cause severe disease with
high mortality in birds. Both HPAI and LPAI viruses can spread rapidly
through poultry flocks. Influenza viruses are constantly changing and
LPAI H7 viruses have been known to rapidly evolve into HPAI viruses.

CDC Risk Assessment

Human infection with avian influenza viruses is rare,
but can occur. Human infections with avian influenza viruses have most
often occurred after unprotected close contact with infected birds or
the excretions/secretions of infected birds (e.g., droppings, oral
fluids). Infected birds shed virus in their saliva, mucous and feces.
Human infections with avian influenza viruses can happen when enough
virus gets into a person’s eyes, nose or mouth, or is inhaled. This can
happen when virus is in the air (in droplets or possibly dust) and a
person breathes it in, or when a person touches something that has virus
on it then touches their mouth, eyes or nose.

At this time no human infections with avian influenza H7N8 viruses have ever been reported worldwide, however other avian influenza H7 viruses have infected people sporadically, including both LPAI and HPAI H7 viruses. H7 virus infections in people have been associated with awide range of illnessfrom conjunctivitis only, to influenza-like illness, to severe respiratory illness.

At this time, CDC considers the risk to the general public from these
H7 viruses to be low; however, because other avian influenza A H7
viruses have infected people, it is possible that human infections with
these viruses could occur. Risk is dependent on exposure. People with
close or prolonged unprotected contact with infected birds or
contaminated environments are likely to be at greater risk of infection.
It is important to note that this is an evolving situation with some
uncertainty. The public health risk assessment and associated
recommendations may change.